TEA2019.PDF

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CURRENT MODE SWITCHING POWER SUPPLY CONTROL CIRCUIT
TEA2019
CURRENT MODE SWITCHING
POWER SUPPLY CONTROL CIRCUIT
. DIRECT DRIVE OF THE EXTERNAL
SWITCHING TRANSISTOR
. POSITIVE AND NEGATIVE OUTPUT CUR-
RENTS UP TO 0.5A
. Automatic input voltage feed-forward in dis-
continuous mode fly-back.
. TRANSFORMER DEMAGNETIZATION AND
POWER TRANSISTOR SATURATION SENS-
ING
. Automatic pulse-by-pulse current limitation.
Typical applications : Video Display Units, TV sets,
typewriters, micro-computers and industrial appli-
cations. For more details, see application
note AN406/0591.
. FULL OVERLOAD AND SHORT-CIRCUIT
PROTECTION
. PROPORTIONAL BASE CURRENT DRIVING
. LOW STANDBY CURRENT BEFORE START-
ING (1.6mA)
. SYNCHRONIZATION CAPABILITY WITH IN-
TERNAL PLL
. THERMAL PROTECTION
DESCRIPTION
The TEA2019 is an 14-pin DIP low cost integrated
circuit designed for the control of switch mode
power supplies. It has the same basic functions as
the TEA2018A but with synchronization capability
by internal PLL. It is particularly suitable for appli-
cations where oscillator synchronization is re-
quired.
DIP 14
(Plastic package)
ORDER CODE : TEA2019
PIN CONNECTIONS
OUTPUT
1
14
NEGATIVE SUPPLY (OUTPUT STAGE)
AUXILIARY OUTPUT SUPPLY
2
13
SUBSTRATE
POSITIVE SUPPLY VOLTAGE
3
12
I SAMPLE (NEGATIVE)
SATURATION SENSING
4
11
GROUND
DEMAGNETIZATION SENSING
5
10
OSCILLATOR CAPACITOR
ERROR AMPLIFIER NON-INVERTING INPUT
SYNCHRONIZATION INPUT
6
9
OSCILLATOR REFERENCE CURRENT
7
8
PLL OUTPUT
August 1992
1/7
. High stability regulation loop.
Due to its current mode regulation, the TEA2019
facilitates design of power supplies with following
features :
. CURRENT LIMITATION
C
11018303.002.png
TEA2019
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V + CC
Positive Supply Voltage
15
V
V (aux)
Auxiliary Output Supply Voltage
15
V
V – CC
Negative Supply Voltage
– 5
V
I O (peak) Peak Output Current (duty cycle < 5%)
±
1
A
I I
Input Current
Pins 4-5
±
5
mA
T j
Junction Temperature
150
°
C
T oper
Operating Ambient Temperature Range
– 20, + 70
°
C
T stg
Storage Temperature Range
– 40, + 150
°
C
2/7
11018303.003.png
TEA2019
THERMAL DATA
Symbol
Parameter
Value
Unit
R th (j-a)
Junction-ambient Thermal Resistance
80
°
C/W
ELECTRICAL OPERATING CHARACTERISTICS
T amb =+25 o C, potentials referenced to ground (unless otherwise specified)
Symbol
Parameter
Min. Typ. Max. Unit
V + CC
Positive Supply Voltage
6.6
8
15
V
V CC
Negative Supply Voltage
–1
–3
–5
V
V CC(start) Minimum positive supply voltage required for starting (V + CC rising)
6
6.6
V
V CC(stop) Minimum positive voltage below which device stops operating (V + CC falling)
4.2
4.9
5.6
V
D
V + CC Hysteresis on V + CC Threshold
0.7
1.1
1.6
V
I CC(sb) Standby Supply Current Before Starting [V + CC <V CC(start) ]
1
1.6
mA
V th (Ic) Current Limitation Threshold Voltage (pin 12)
–1100 –1000 –880 mV
R (Ic )
Collector Current Sensing Input Resistance
1000
W
I S
Demagnetization Sensing Threshold
75
100
125
mV
Demagnetization Sensing Input Current (pin 5 grounded)
1
m
A
t
max
Maximum Duty Cycle
70
80
%
A V
Error Amplifier Gain
50
I + I
Error Amplifier Input Current (non-inverting input) (pin 6)
2
m
A
V (REF) Internal Reference Voltage
2.3
2.4
2.5
V
D
V ( REF )
D
Reference Voltage Temperature Drift
10 –4
V/
°
C
T
T OSC Oscillator Free-running Period ( R = 59k
W
, C = 1.5nF)
60
65
70
m
s
D
f OSC
D
Oscillator Frequency Drift with Temperature (V + CC = + 8V)
0.05
%/
°
C
T
D
f OSC
D
Oscillator Frequency Drift with V + CC (+ 8V < V + CC < + 14V)
0.5
%/V
V CC
t on(min) Minimum Conducting Time (C t = 1nF)
2
m
s
SYNCHRONIZATION INPUT (pin 7)
Symbol
Parameter
Min.
Typ. Max. Unit
V 7pp
Peak to Peak Sawtooth Voltage
0.5
2.5
V
R (7)
Input Impedance
20
k
W
PLL CHARACTERISTICS (see Test Circuit)
Symbol
Parameter
Min. Typ. Max. Unit
Frequency Sensitivity
100
Hz/ m A
D
T
Capture Range (T OSC =64
m
s Typ.)
T OSC -T SYN min
5.5
4.5
8
8
m
s
T SYN max -T OSC
m
s
SATURATION SENSING (pin 4)
Symbol
Parameter
Min.
Typ. Max. Unit
V (4)
Input Threshold
3.2
V
I (4)
Input Current (V 4 > 3.2V)
50
m
A
Input Internal Resistance
1
k
W
RECOMMENDED OPERATING CONDITIONS
Symbol
Parameter
Min.
Typ. Max. Unit
V + CC
Positive Supply Voltage
8
V
V CC
Negative Supply Voltage
3
V
I O
Output Current
0.5
A
F oper
Operating Frequency
30
kHz
3/7
11018303.004.png
TEA2019
TYPICAL CIRCUIT
V6
V5
V3
22nF
470
W
10
W
10nF
AS1
22nF
4.7
m
F
8.2k
W
10nF
7
6
5
4
3
2
1
10k
W
RAMP
GENERATOR
IC
TEA2019
0V
8
9
10
11
12
13
14
-1V
22nF
4.7
F
59k
W
56k
W
1%
3.9k
W
1.5nF
3.3nF
100
W
47nF
V10
V12
V14
GENERAL DESCRIPTION
(see application note AN406/0591)
Figure 1 : Current Mode Control
Operating Principles (Figure 1)
On every period, the beginning of the conduction
time of the transistor is triggered by the fall of the
oscillator saw-tooth which acts as clock signal. The
period T osc is given by :
T osc
V i
FLIP-FLOP
OUTPUT
FILTER
OSCILLATOR
S
I C
9 0.69 C t (R t + 2000)
(T osc in seconds, C t in Farad, R t in W )
The end of the conduction time is determined by a
signal issued from comparing the following signals.
a) the sawtooth waveform representing the
collector current of the switching transistor,
sampled across the emitter shunt resistor.
b) the output of the error amplifier.
Base Drive
• Fast turn-on
On each period, a current pulse ensures fast
transistor switch-on.
This pulse performs also the t on(min) function at
the beginning of the conduction.
ERROR
AMPLIFIER
Q
V REF
ERROR
SIGNAL
R
COMPARATOR
Re
C I SENSE
OSCILLATOR
SAWTOOTH
t
Proportional base drive
In order to save power, the positive base current
after the starting pulse becomes an image of the
collector current.
The ratio I C
I B
Error
Signal
I (sample)
t
is programmed as follows (Figure 2).
FLIP-FLOP
OUTPUT
I C
I B
=
R B
R E
t
4/7
m
•
C
11018303.005.png
TEA2019
• Efficient and fast switch-off
When the positive base drive is removed, 1s
(typically) will elapse before the application of
negative current therefore allowing a safe and
rapid collector current fall.
• Demagnetization sensing
This function disables any new conduction cycle
of the transistor as long as the core is not com-
pletely demagnetized.
When not used, pin 5 must be grounded.
• t on(max)
Outside the regulation area and in the absence
of current limitation, the maximum conduction
time is set at about 70% of the period.
Safety Functions
• Overload & short-circuit protection
When the voltage applied to pin 12 exceeds the
current limitation thershold voltage [V th(Ic) ], the
output flip-flop is reset and the transistor is turned
off.
The shunt resistor R e must be calculated so as
to obtain the current limitation threshold on pin
12 at the maximum allowable collector current.
t on(min)
A minimum conducting time is ensured during
each period (see Figure 2).
• Supply voltage monitoring
The TEA2019 will stop operatingif V CC +onPin3
falls below the threshold level V CC(stop) .
Figure 2
I C
COLLECTOR
CURRENT
I C
0
t
I C
I B
t on(min)
R B
BIAS
CURRENT
TEA2019
1
I B
R B
I B
I C
12
R e
R e
0
t
Starting Process (Figure 3)
Prior to starting, a low current is drawn from the
high voltage source through a high value resistor.
This current charges the power supply storage
capacitor of the device.
No output pulses are available before the voltage
on pin 3 has reached the threshold level [V CC(start) ,
V + CC rising].
During this time the TEA2019 draws only 1mA
(typically). When the voltage on pin 3 reaches this
threshold base drive pulses appear.
The energy drawn by these pulses tends to dis-
charge the power supply storage capacitor. How-
ever a hysteresis of about 1.1V (typically) ( D V CC )
is implemented to avoid the device from stopping.
Figure 3 : Normal TEA2019 Start up Sequence
V CC
V CC (start)
6V
4.9V
V CC
V
CC (stop)
t
5/7
•
11018303.001.png

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